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There are two rubber plugged ports on the right side of my Holley - one big one toward the rear and a smaller one up on the metering block. To which does the vacuum advance line attach? Does that port on the metering block actually supply vacuum? It's the right size for a vac. ad. hose.
 

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IME, the port above the idle mixture screw on the passenger side of the primary metering block is where the vacuum advance goes. This is ported vacuum, which is created by airflow in the primary venturi.

The big one, in the throttle plate IIRC, is ported to intake manifold vacuum and can be used for PB or PCV if no port/spacer is available.

I'd have to see a picture to be sure...hope that helps!
 
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I prefer to hoo vacuum advance to manifold vacuum rather than venturi vacuum. It all depends on how you have you engine set up and if you fully understand what is going on. On a performance type engine, you do not need vacuum advance. All your ignition tuning and total advance can be done with centrifugal and initial only. It will also be very stable like this. Use the vacuum advance for better gas mileage. When you attach it to manifold vacuum, the vacuum advance willl do nothing when you have the throttle floored. Your initial and centrifugal advance will creat your total advance. When you let up and are cruising, manifold vacuum is high, it will advance your timing and allow better fuel mileage. Manufacturers have done it both ways stock. Although they usualy use temperature controlled vacuum trees to further complicate the situation: emissions.
 
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